Metal-coatings tester



A. S, CUSHMAN. METAL COATINGS TESTER.

APPLICATION FILED FEB. s. 1920. 1,372,405, Patented Mar. 22, 1921.

Ihre/liar.-

UNITED STATES PATENT OFFICE.

ALLERTON S. CUSHMAN, OF WASHINGTON, DISTRICT 0F COLUMBIA.

Mn'rancoa'rrnes TESTER.

Specification of Letters Patent.

Patented Mar. 22, 1921.

Application `filed February 6, 1920. Serial No. 356,683.

To all whom 'it may concern i v Be it known that I, tLLnnroN S. GUsT-T-MAN, a citizen of the United States, residing at lllashington, in theDistrict of Columbia,

have invented certain new and useful Im-` mensions, and dissolve off thecoating in hydrochloric acid in which a certain quantity of chlorid ofantimcny is dissolved. The object of the chlorid of antimony is toprevent the acid from attacking the iron or steel base after it hasdissolved off the metallic coating such as may be represented by zinc,tin, or terne coinlziosition.` There is nothing new or novel in the useof antimony chlorid for this purpose. I confine myself in my claims forinvention to the apparatus which I have designed with the followingobiect.

By my method it is not necessary` to cut specimens of accurate dimensiono r length from the coated metal under investigation, and thereaftergoto thel expense of time and money in accurately measuring or machiningthe specimen to a specified length or area. The object of my inventionis to provide a glass apparatus as illustrated, which can be placed uponthe surface of coated sheet metal at any desired spot, and by letting inthe` acid onto the spot, strip the zinc coating, collect the hydrogengas evolved by the reaction in a tube so suitably graduated that thevolume of hydrogen measured will accurately measure the weight ofprotective coating in ounces per square foot or in any other 'desiredsystem of prescribing the Weight per unit surface.

I now refer to the attached sketch of my 'apparatus which is constructedentirely of glass except for the rubber Stoppers shown on the sketch atE and F. A is a glass vessel provided with flanges at the base B,accurately ground so as to be flat and true. By smearing the flange at Bwith a thin film of desiccator grease, it can be placed on the surfaceof coated sheet metal and pressed down so that the joint at B ispneumatically sealed to a slight head of liquid contained in the vesselA. Having irst sealed the apparatus to the surface as described, a knownquanclosed, cock lvl is opened, which allows the tityof hydrocholricacid (1.20 sp. gr.) containing a small quantity of antimony chlorid 1nsolution is placed in the thistle tube C. In the meantime, the deliverytube G may be connected with a piece of rubber tubing terminating in aglass elbow delivery tube.`

The glass elbow Ydelivery. tube is inserted under the bottom ofthegraduated collection tube Kwhich is set on a stand in a basin of water.The tube K is entirely filled with water by suction through the tube Mwhich is connected `with Il by the stopoock L. TWhen all is ready, thestopcock I being acid in C to completely run into the vessel it..Stopcoclr Il is immediately closed. In

` about two minutes the metallic coating is stripped from the spotcovered on the sheet by the `Hangs B, and the hydrogen gas passed overinto the collection tube K where its volume is read off and recorded.The glass elbow delivery tube is then removed and stopcockI opened. Byblowing through l tube G and opening stopcoclr I, the ex- -haustedacidis blown out of A, passing out oftube J into a suitable glass vessel.Fresh water is thenlet down through C and H to rinse the remaining acidout of A and the rinsing water again blown out at J. lIhe apparatus canthen be lifted to a new spot, if itis desired to explore the weight ofcoating on different parts of the same sheet. v

If the apparatus is to be used for determining the weight of coating onsay gal-` vanized wire, a definite length of wire of known gage is cntinto pieces of suitable length, and placed underneath the aplvnaratus invessel A. In this case, however, a ground glass base is used. instead.of the sheet metal as hereinbefore described. In the same way, coatediron and steel objects of suitable :size can be placed in A when it isdesired to determine the weight of coating which they carry.

By use of this apparatus, I am enabled to determine the weight ofcoating on any desired surface in a very few minutes, thus avoiding thecostly and time consuming process of preparing specimens by cutting outsections from 4surfaces of heavy sheet metals, and thereafter havingthem accurately machined to known specific areas. I can 'also explorethe weight of coating` on all parts of both sides of full sizecommercial sheets of all gages, Without cutting or del. l. U

stroying the sheets, as happens in the usual method of testing, so thatfull size commer-V cial sheets after having been tested with myapparatus can' be re-pickled and re-run at the factor7 without wastingor cutting out or otherwiseinjuring the sheet. By my method I can fullyexplore the weight of y my apparatus and find that it gives readandweighing.

ings of a greater degree of accuracy than the more tedious process ofcutting, stripping I wish to have it understood that the foregoingdisclosure has been made solely for the purpose of explaining the natureof the invention and the principles upon which it is based.4 I havereferred, for the sake of convenience, to the application of a form ofmy invention to a plane surface. VI am, however, in no vwise limitedthereto. The inven tion is applicableto any surface, whatever itscharacter may be. It is merely necessary to employ a vesselcorresponding to vessel A whichv has its'open end shaped to fit thecontour of the surface to be tested.Y For instance, in order to explorethe surface of an alreadyV formed corrugated surface I would use aconvoluted templet designed to it the corrugations and towhich thevessel A is made to adhere. This templet may be fashioned out of hardrubber or out of glass or any other suitable material properly formedand ground to fit the standard size corrugations. generally used. Forfield use it is even desirable to make theV templet of iron or othermetals to decrease the danger of break` ing. The action of the acid uponthe coat ing is so rapid in comparison with its action upon variousother metals and the test period so short that these metals may be usedwith safety. 4 It is not necessary to go into detail as to the variousdetails of adapting the' vessel A to surfaces of various forms as thisis a matter of common knowledge and does not affect the essence of lnyinvention.

While I have shown a particular arrangement for making communicatingconnections to the vessel A, it is understood that these connections maybe made in various other ways within the scope of the invention. Thevessel A might for instance be closed at the top by a stopper with threeholes to permit the insertion of tubes corrcspending to C, D and G.

lWhile I have specifically referred to one way of providing a sealbetween the vessel A and the surface' of the element to bc tested, theinvention is by no means identii'ied therewith. It is obvious that aseal may be provided in various other ways.

I claim:

1. The process of determining the weight of metallic coatings on ironand steel structures, which consists in applying hydrochloric acid to adefinite integral portion of the coated surface of the structure andmeasuring the volume of gas evolved by the action of the acid.

2. Apparatus for determining the weight of metallic coatings of iron andsteel structures a situ, comprising a receptacle open at its bottom,means at its top for introducing a liquid and means for drawing off gasevolved therein.

3. Apparatus for determining the weight of metallic coatings of iron andsteel structures n situ, comprising a receptacle open at its bottom andhaving at its top a stopper opening adapted to receive a thistle tubeand an outlet for gas evolved in the receptacle.

4;. Apparatus for determinino the weight of metallic coatings of ironan' steel structures a s-tu, comprising a receptacle having an openbottom, a stopper opening at its top and an outlet for gas evolved inthe receptacle, and a thistle tube adapted to be iuserted into saidstopper opening.

In testimony whereof I affix my signature.

ALLERTON S. CUSHMAN.

